Method for forming loops on coil springs



Nov. 21, 1961 T. K. RIGGEN ETAL METHOD FOR FORMING LOOPS ON con. SPRINGS Filed Jan. 2, 1958 INVENTORS THEODORE K. R/GGEN W/ LBURN L. PETERSON United States Patent 3,009,490 METHOD FOR FORMING LOOPS ON COIL SPRINGS Theodore K. Riggen, 922 Bridgman St, Elmira, N.Y.,

and Wilhurn L. Peterson, 277 Cherry Hill Drive,

Newington, Conn.

Filed Jan. 2, 1958, Ser. No. 706,824 6 Claims. (Cl. 140-403) This invention relates to a method for forming loops on coil springs generally and particularly on small size tension springs. Such springs are used in large numbers on typewriters, adding machines, and many other devices.

Springs to which this invention pertains are customarily made of spring wire having any desired diameter up to about No. 16 wire. The springs may be made in any length, the coils having any desired diameter up to as much as half inch or larger. Most coil springs to which this invention may be applied are of the size usually found on typewriters, adding machines and similar devices wherein the spring coil may have a diameter up to about one quarter inch, while the wire itself may have a diameter of about 0.015 inch. These figures are exemplary and it is to be understood that larger and smaller springs of heavier and finer gauge wire may be operated upon.

The invention to be described may be applied to any type of tension spring of generally small size, wherein a spring length is to have end loops of the side, center or crossover type. The invention generally has little application to large size springs because they are generally manufactured in a different manner from small size springs and permit more care to be exercised in the formation of the end loops. In so far as large size springs may be manufactured similarly to small springs, the invention may be applied to such large springs.

Small size springs are generally formed in coils of indefinite lengths on suitable spring coiling machines. Such machines are well known in the trade and require no description. The coil springs in indefinite length are fed to a cutting machine for cutting the springs to desired length. Such machines may incorporate means for forming an end loop at one or both ends of the spring.

For convenience, the word spring itself will be used in connection with a length of coil spring which has been cut to a predetermined length. Such spring usually has ends to be shaped to provide suitable loops for mounting the springs for use. Where an indefinite length of spring is referred to, the expression indefinite length of coil spring will be used.

Coil springs usually require end loops so that each spring may be attached between spaced supports to permit the spring to function. The most common and cheapest loop for a coil spring is the regular side loop wherein one or two end coils of a spring are bent out of normal position, the bending being at right angles. The end loop of such a spring will lie in a plane which is tangent to the coils of the body of the spring and thus be offset from the coil axis. Such springs are made in great quantity and are widely used. The loading of a spring with such an off-set loop is not satisfactory for many purposes and renders such springs unusable.

In an effort to improve spring loading, it is possible to provide a crossover loop. A crossover loop consists of one or two coils lying in a plane containing the axis of the coil spring. A crossover loop may be regarded as an off-set loop which has been translated toward the center of the coil springs to render the loops symmetrical to the springs coils.

The practice in the manufacture of such crossover loops has been first to form a regular side loop and then move the loop toward the center line of the coil spring by suitable tools. This procedure results in difiiculties both with regard to production and with regard to the finished spring. These difliculties are reflected in the increased market price for crossover loop springs.

Another difiiculty relates to the tools used in forming loops. Present-day methods and machines require forming tools which inherently do not have a long useful life. In most instances, the tools have geometrically complex surfaces and edges. Consequently, when a tool edge begins to wear, the shape of the tool is such that expensive grinding is required for renewing the tool. Additionally, a substantial length of tool must be removed in order to maintain the predetermined relationship of the various forming surfaces and edges.

In accordance with this invention, a method of loop formation is provided which eliminates the difficulties to both the product and the forming tool. An additional advantage of the present invention resides in the flexibility of production so that simple changes only are required to turn out springs having end loops of various dimensions and angles. In present-day machines, the geometry of the forming tools precludes changing loop shapes by mere adjustment of tool travel.

In general, the new method reverses the order of the steps for forming crossover loops on springs as presently practiced. Furthermore, the new method makes it possible to provide any desired degree of orientation of the crossover loop at one end of the spring with respect to the crossover loop at the other end of the same spring.

By virtue of the new method, an apparatus for making springs makes it possible to use forming tools having simple forming surfaces. The forming tools have active forming surfaces which are linear and resemble a simple chisel. Thus the reforming of the tools edge becomes a simple grinding operation and does not remove any more metal than would be necessary for the grinding of a simple chisel.

In accordance with the new method, one or two end coils of a length of coil spring is translated bodily from the main body of the spring, the translated coils, however, remaining generally in planes normal to the original axis of the coil spring. Thereafter, the end coil or coils are formed normal to their original position, the forming or twisting step disposing the translated coil or coils along the axis of the coil spring so that a full formed crossover loop results. By virtue of this reversal of steps, sharp bending of the coil spring Wire is avoided and any desired configuration for crossover loop may be provided. The spring wire joining the coil spring and the loop proper may be shaped to provide a gentle curve or turn, thus not only making a strong spring but improving the loading characteristics of the spring.

The new method retains the coil spring in position without dropping while operating successively on one end and then upon the other end of the coil spring for the forming of the crossover loop. This makes it possible to orient the plane of each crossover loop at each end of the coil spring. This is important where it is desired to have some control over the relative positioning of the crossover loops at the two ends of the coil spring.

The new method makes it possible to feed the coil spring through a die plate having an opening which need not be accurately dimensioned in relation to the spring itself. This is in sharp contrast to present-day methods and machines wherein an accurate die plate is necessary.

In general, an indefinite length of coil spring is fed through an apertured die plate by suitable means. The crossover loop forming portion of the end of the coil spring, this consisting of between one and two turns as a rule, is permitted to extend through the die plate aperture. A number of forming tools, each one of which generally resembles a guillotine, are suitably operated 3 so that the loop coil is first translated and then bent into the proper plane.

In order that the invention may be fully understood, reference will now be made to the drawings wherein:

FIGURES l to 5 inclusive are perspective views of the crossover loop forming tools in various stages of operation from the beginning to the end of a loop formation to illustrate the various steps in the method.

A floating plate consists of a generally rectangular steel plate having aperture 11 therethrough for accommodating work 12. Work 12 will consist either of a portion of an indefinite length of coil spring or a finite length of coil spring after the same has been severed from the parent body. In general, plate 10 may have any desired extent and is disposed so that the plane thereof is perpendicular to the axis of spring 12. Aperture 11 through the plate is preferably somewhat larger than the outside diameter of spring 12 and is preferably circular. The ratio of diameter of aperture to the outside diameter of spring 12 is not critical and may, for example, range from somewhat over 1 to as much as 1.2.

It should be noted that the forward end of spring 12 will have been cut when the same is operated upon. Spring 12 and plate 10 are so related relative to each other during the looping operations that a predetermined number of spring coils extend beyond the active face of plate 16 in the region to be operated upon by the looper mechanism. Spring 12 has about one coil extending beyond active face 10:: of plate 10, this being in a region for operation by the loop-forming mechanism. The amount of spring material extending beyond the active face of plate 10 may vary as desired, and in general will range from about one coil to about two coils. Somewhat less than one coil may be used for special loops. The same may be true of situations where more than two coils may be desired.

The loop-forming means includes tool 15 having chiselshaped coil-selection blade 16 and loop stop portion 17. Tool 15 is adapted to move along its length to overlie aperture 11. It will be noted from FIGURE 3 that tool 15 does not completely cover aperture 11 but is offset so that side 18 of tool 15 leaves an open space for aperture 11 within which the spring wire may adjust itself in response to the loop-forming operation. The width of tool 15, however, is greater than the diameter of aperture 11 so that side 19 of the tool opposite side 18 is disposed on the solid portion of plate 10 beyond the aperture.

Tool 15 is formed of tool steel. The angle of coil selection blade portion 16 may vary within limits. The thickness of tool 15 will vary within wide limits depending upon the diameter of the coil spring and the chisel angle of portion 16. Tool 15 moves up as illustrated in FIGURE 2, blade 16 entering between adjacent spring coils. As seen in FIGURE 2, stop portion 17 of the tool may engage the bottom of the coil before chisel edge 16 has reached the top of the coil. As illustrated in FIG- URE 3, further movement of tool 15 upwardly of the coil causes the end coil to be twisted in an anti-clockwise direction.

When tool 15 has completed its motion, tool 22 starts its motion toward off-set loop 12b. It is understood that both tools 15 and 22 have the active portions thereof travelling along the face of plate 10, in this instance face 10a. Tool 22 has active chisel-shaped edge 23 which comes in under loop 12b of the spring. Tool 22 has steep rising slope 24 from edge 23, this slope extending away from plate 10. Thus as tool 22 moves downwardly into the work, coil 12b of the spring is twisted outwardly by the cam action of face 24. While the angle of face 24 may suffice to cause loop 12b to be turned outwardly for a substantial degree, a control of the amount of turn to be imparted to the loop is obtained by rocking tool 22. Thus tool 22 is secured on pin 26 and by virtue of means to be described later, tool 22 is rocked anti-clockwise as .seen in FIGURES 1 to 4 inclusive. Thus active edge 23 of tool 22 will force loop 12b of the spring to move into a position where the plane of coil 12b is generally perpendicular to its original plane before upsetting and turning.

It is clear that by controlling the directions of travel of tools 15 and 22 with respect to each other, by controlling the amount of spring material extending beyond the active face of plate 10, by controlling the amount of travel of tool 15 with respect to the spring, and by controlling the various tool shapes that a wide variety of loops may be formed on the same spring or on different types of springs.

FIGURE 5 shows the loop formation from a different angle and illustrates the cam action of tool 22 in operating upon the loop.

The position of the loop-forming tools as illustrated in FIGURE 4, this marking the completion of a loop formation, results in a firm grip being retained upon spring 12. However, the exact location in space of the main body of coil spring 12 is unimportant.

What is claimed is:

l. A method of providing a loop on the end of a helical coil spring comprising laterally offsetting at least part of the end coil along a line substantially perpendicular to the axis of the helix for less than the helix diameter and thereby bending a connecting curved portion extending between the olfset part and the body of the helix to a somewhat sharper curve to move said connecting portion so that it extends across the end of the helix and thereafter twisting said offset part through an angle of substantially about the connecting portion as an axis so that the upset coil axis and helix axis are substantially perpendicular and intersecting, the only operation involving twisting of the wire being distributed over the length of said connecting portion whereby crystallization of the spring wire between the helix and the end loop is substantially avoided.

2. A method of providing a loop on the end of a helical coil spring, said method comprising translating at least part of the end coil along the axis of the helix without changing the circular character of the coils, laterally olfsetting the translated coil portion along a line generally perpendicular to the axis of the helix for less than the helix diameter and thereby bending a connecting curved portion extending between the offset part and the body of the helix to a somewhat sharper curve to move said connecting portion so that it extends across the end of the helix and thereafter twisting said offset portion about 90 about the connecting portion as an axis, the only operation involving any substantial twisting of the wire being distributed over the length of said connecting portion whereby crystallization of the spring wire between the helix and the end loop is substantially avoided.

3. A method of providing a loop on the end of a helical coil spring which comprises supporting the body of the coil spring against lateral movement while leaving at least part of one end coil unsupported, exerting a force on said unsupported part in a direction perpendicular to the axis of the helix to offset said unsupported part laterally from the helix for less than the helix diameter and thereby causing a portion of the spring wire connecting the offset part and the body of the helix to extend across the end of the helix, supporting said connecting portion against movement back to its original position and exerting force upon the laterally offset part to twist and move it about the connecting part as an axis through an angle of substantially 90 to a position where the twisted coil axis and helix axis are substantially perpendicular and intersecting, said connecting portion extending generally diametrically across the helix and the twisting of said wire being distributed over the length of the connecting portion to avoid crystallization.

4. The method according to claim 3 wherein said second named force is exerted at a portion of the offset part which is outside of the cylindrical surface defined by the helix.

5. The method according to claim 3 wherein said 1; A -dlL first named force is exerted at one region of the unsupported coil part and wherein said second named force is initially exerted along the extension of a coil diameter going from the point of application of the first named force.

6. A method of providing a loop on the end of a helical coil spring which comprises supporting the body of the coil spring against lateral movement while leaving an end portion of the coil spring unsupported, pushing a chisel-shaped member against the unsupported spring coils along a line passing through the axis of the helix and perpendicular thereto to move the unsupported spring portion so that it is laterally offset from the body of the helix, the amount of offset being less than the helix diameter so that the offset coil overlays part of the region enclosed by the prolongation of the References Cited in the file of this patent UNITED STATES PATENTS 046,497 Lamb et al. Apr. 3, 1900 2,078,828 vBaer et a1. Apr. 27, 1937 2,420,512 Woller May 13, 1947 2,624,377 Smith June 6, 1953 2,703,592 Penny Mar. 8, 1955 

